Polycarbonate compositions having improved flame retardance and improved water vapor transmission

ABSTRACT

Improved flame retardance and improved water vapor transmission are imparted to high molecular weight aromatic polycarbonate resins by selecting appropriate diphenols and controlling the degree to which these particular diphenols are halogenated.

This invention relates to aromatic polycarbonate resins having improvedflame retardance and improved water vapor transmission.

BACKGROUND OF THE INVENTION

Polycarbonate polymers are known as being excellent molding materialssince products made therefrom exhibit such properties as high impactstrength, toughness, high transparency, wide temperature limits (highimpact resistance below -60° C. and a UL thermal endurance rating of115° C. with impact), good dimensional stability, good creep resistance,and the like. It would be desirable to add to this list of propertiesthat of improved flame retardance so that products made from suchpolycarbonate polymers could be safely used by the consumer and alsomeet the increasing requirements of certain flame retardant criteriabeing established by local and federal government agencies as well asthe manufacturers of such products. It would also be desirable toimprove the moisture barrier property of such polycarbonates therebyenabling them to be used in a wider range of product applications.

It is known to obtain polycarbonates which contain halogenated monomersas their main, polymeric building blocks. For example, U.S. Pat. No.3,028,365 discloses a host of polycarbonate compositions includingtetrabromobisphenol-A and a dichloromethylenediphenol monomer, as wellas processes for obtaining these polycarbonates.

U.S. Pat. No. 3,062,781 discloses that halogenated polycarbonates can beobtained by first halogenating a diphenol containing at least twohalogen substituents. However, the only dihalogenated diphenol disclosedis dichlorobisphenol-A.

German Pat. No. P25 20 317.2 discloses that halogenated polycarbonatescan be obtained by halogenating bisphenol-A(4,4'-isopropylidenediphenol) to produce a mixture of unreactedbisphenol-A and statistical mixtures of halogenated bisphenol-A (BPA).The halogenated bisphenols disclosed comprise, primarily, tri- andtetrahalogenated BPA.

In general, these prior art references recognize that flame retardancecan be imparted to polycarbonates by halogenating the monomeric buildingblocks from which they are obtained. In addition, these referencessuggest that the greater the degree of halogenation of the monomer, thebetter will be the fire retardance imparted to the polymer. U.S. Pat.No. 3,062,781 also indicates that halogenated diphenols have reducedpermeability to steam. However, none of these references discloses orsuggests that a high molecular weight aromatic polycarbonate resinhaving improved flame retardance as well as improved water vaportransmission can be obtained from particular halogenated diphenols.

SUMMARY OF THE INVENTION

It has now been found that improved flame retardance and water vaportransmission can be imparted to high molecular weight, aromaticpolycarbonate resins by selecting appropriate diphenols to behalogenated. In general, this is accomplished by controlling the degreeto which the particular diphenols are halogenated. Accordingly, thediphenols are halogenated so that there are obtained either highly puredihalogenated diphenols or predetermined statistical mixtures comprisingpredominantly mono- and dihalogenated diphenols together with someunreacted diphenol.

Preferably, these predetermined, statistical, halogenated diphenolmixtures can be continuously obtained by either: (1) dissolving orsuspending the diphenol in a solvent system comprising methylenechloride and water and thereafter introducing a halogen into the solventsystem; or, (2) dissolving or suspending the diphenol in methylenechloride and then reacting the diphenol with sulfuryl chloride and,optionally, introducing another halogen therein; or, (3) dissolving orsuspending the diphenol in methylene chloride and then introducing ahalogen therein while concurrently purging the reaction with an inertgas. These processes are described in co-pending applications Ser. No.882,192, filed Feb. 28, 1978, Ser. No. 882,242, filed Feb. 28, 1978, andSer. No. 882,191, filed Feb. 28, 1978, respectively, all of which areassigned to the same assignee of this case.

While any of the halogens can be employed, chlorine and bromine arepreferred. Thus, the diphenols that can be used to obtain the highmolecular weight aromatic polycarbonates of the invention can berepresented by the general formula ##STR1## wherein Xm and Xn can eachindependently be a halogen and mixtures thereof; m and n are each 0.0 toabout 2.5 with the proviso that m+n equal at least 0.1 and not more thanabout 2.5; and, Y and Y' can independently be hydrogen and a halogen,preferably chlorine or bromine. In formula I above, the values for m andn represent the number of halogen substituents per mole of monomer.

It is possible to employ two or more different diphenols or a copolymerwith a glycol or with hydroxy or acid terminated polyester, or with adibasic acid in the event a carbonate copolymer or interpolymer ratherthan a homopolymer is desired for use in preparing the aromaticpolycarbonate. Blends of any of these materials can also be used toobtain the aromatic polycarbonates.

These halogenated diphenols can then be employed to obtain the highmolecular weight aromatic polycarbonates of the invention which can belinear or branched homopolymers or copolymers as well as mixturesthereof or polymeric blends and which generally have an intrinsicviscosity (IV) or about 0.40-1.0 dl/g as measured in methylene chlorideat 25° C. These high molecular weight aromatic polycarbonates can betypically prepared by reacting the halogenated diphenol with a carbonateprecursor.

The carbonate precursor used can be either a carbonyl halide, acarbonate ester or a haloformate. The carbonyl halides can be carbonylbromide, carbonyl chloride and mixtures thereof. The carbonate esterscan be diphenyl carbonate, di-(halophenyl) carbonates such asdi-(chlorophenyl) carbonate, di-(bromophenyl) carbonate,di-(trichlorophenyl) carbonate, di-(tribromophenyl) carbonate, etc.,di-(alkylphenyl) carbonate such as di(tolyl) carbonate, etc.,di-(naphthyl) carbonate, di-(chloronaphthyl) carbonate, phenyl tolylcarbonate, chlorophenyl chloronapthyl carbonate, etc., or mixturesthereof. The haloformates that can be used include bis-haloformates ofdihydric phenols (bischloroformates of hydroquinone, etc.) or glycols(bishaloformates of ethylene glycol, neopentyl glycol, polyethyleneglycol, etc.). While other carbonate precursors will occur to thoseskilled in the art, carbonyl chloride, also known as phosgene, ispreferred.

Also included are the polymeric derivatives of a dihydric phenol, adicarboxylic acid and carbonic acid such as are disclosed in U.S. Pat.No. 3,169,121 which is incorporated herein by reference.

Molecular weight regulators, acid acceptors and catalysts can also beused in obtaining the aromatic polycarbonates of this invention. Theuseful molecular weight regulators include monohydric phenols such asphenol, chroman-I, paratertiarybutylphenol, parabromophenol, primary andsecondary amines, etc. Preferably, phenol is employed as the molecularweight regulator.

A suitable acid acceptor can be either an organic or an inorganic acidacceptor. A suitable organic acid acceptor is a tertiary amine such aspyridine, triethylamine, dimethylaniline, tributylamine, etc. Theinorganic acid acceptor can be either a hydroxide, a carbonate, abicarbonate, or a phosphate of an alkali or alkaline earth metal.

The catalysts which can be employed are those that typically aid thepolymerization of the diphenol with phosgene. Suitable catalysts includetertiary amines such as triethylamine, tripropylamine,N,N-dimethylaniline, quaternary ammonium compounds such as, for example,tetraethylammonium bromide, cetyl triethyl ammonium bromide,tetra-n-heptylammonium iodide, tetra-n-propyl ammonium bromide,tetramethylammonium chloride, tetramethyl ammonium hydroxide,tetra-n-butyl ammonium iodide, benzyltrimethyl ammonium chloride andquaternary phosphonium compounds such as, for example, n-butyltriphenylphosphonium bromide and methyl triphenyl phosphonium bromide.

Also included herein are branched polycarbonates wherein apolyfunctional aromatic compound is reacted with the diphenol andcarbonate precursor to provide a thermoplastic randomly branchedpolycarbonate. These polyfunctional aromatic compounds contain at leastthree functional groups which are carboxyl, carboxylic anhydride,haloformyl, or mixtures thereof. Illustrative of polyfunctional aromaticcompounds which can be employed include trimellitic anhydride,trimellitic acid, trimellityl trichloride, 4-chloroformyl phthalicanhydride, pyromellitic acid, pyromellitic dianhydride, mellitic acid,mellitic anhydride, trimesic acid, benzophenonetetracarboxylic acid,benzophenonetetracarboxylic anhydride, and the like. The preferredpolyfunctional aromatic compounds are trimellitic anhydride andtrimellitic acid or their acid halide derivatives.

Blends of linear and branched aromatic polycarbonates are also includedwithin the scope of this invention.

Other well known materials can also be employed for their intendedfunction and include such materials as anti-static agents, mold releaseagents, thermal stabilizers, ultraviolet light stabilizers, reinforcingfillers such as glass and other inert fillers, foaming agents, and thelike.

Accordingly, the high molecular weight aromatic polycarbonates of theinvention can be represented by the general formula ##STR2## wherein Xm,Xn, m, n, Y and Y' are the same as identified in formula I above.

PREFERRED EMBODIMENT OF THE INVENTION

The following examples are set forth to more fully and clearlyillustrate the present invention and are intended to be, and should beconstrued as being, exemplary and not limitative of the invention.Unless otherwise stated, all parts and percentages are by weight.

In the following examples, the flame retardancy of the polycarbonatesobtained was determined by feeding the polycarbonates into an extruderwhich was operated at about 265° C. and the extrudates were eachcomminuted into pellets. The pellets were then injection molded at about315° C. into test bars of about 5 in. by 1/2 in. by about 1/16-1/8 in.thick. The test bars (5 for each polycarbonate) were then subject to thetest procedure set forth in Underwriter's Laboratories, Inc. BulletinUL-94, Burning Test for Classifying Materials. In accordance with thistest procedure, materials so investigated are rated either V-0, V-I,V-II based on the results of 5 specimens. The criteria for each V (forvertical) rating per UL-94 is briefly as follows:

"V-0": Average flaming and/or glowing after removal of the ignitingflame shall not exceed 5 seconds and none of the specimens shall dripflaming particles which ignite absorbent cotton.

"V-I": Average flaming and/or glowing after removal of the ignitingflame shall not exceed 25 seconds and the glowing does not travelvertically for more than 1/8" of the specimen after flaming ceases andglowing is incapable of igniting absorbent cotton.

"V-II": Average flame and/or glowing after removal of the igniting flameshall not exceed 25 seconds and the specimens drip flaming particleswhich ignite absorbent cotton.

In addition, a test bar which continues to burn for more than 25 secondsafter removal of the igniting flame is classified, not by UL-94, but bythe standards of the instant invention, as "burns". Further, UL-94requires that all test bars in each test group must meet the V typerating to achieve the particular classification. Otherwise, the 5 barsreceive the rating of the worst single bar. For example, if one bar isclassified as V-II and the other four (4) are classified as V-0, thenthe rating for all would be V-II.

The moisture barrier properties for the polycarbonates andcopolycarbonates in the ensuing examples were determined using ModernControls, Inc. instruments, i.e., water vapor transmission rate (WVTR)measurements were obtained on an IRD-2C instrument pursuant to ASTMF-372-73. This method is based on infrared analysis and the resultsobtained are expressed in grams/24 hrs./100 in.² /mil at 100° F. and 90%relative humidity (RH).

EXAMPLE 1 Preparation of a New Compound:2,2'-Dichloro-4,4'-(dichlorovinylidene)diphenol (DCDVD)

Into a slurry of 281.14 parts by weight (1.0 partmole) of4,4'-(dichlorovinylidene)diphenol (DVD) in 2000 parts by volumemethylene chloride that was purged continuously with a slow stream ofnitrogen, there was introduced, at ambient temperature, in the course ofca. 5 hours, 142 parts by weight (2.0 partmole) of chlorine gas. At theend of the slightly exothermic reaction, only a small amount of DVDremained undissolved. This was filtered off and the essentiallycolorless solution was analyzed by gas chromatography, which indicatedthe following composition:

    ______________________________________                                                              Retention                                                                              Compo-                                                               Time     sition                                         Compound              (Min.)   (Mole %)                                       ______________________________________                                        4,4'-(dichlorovinylidene)diphenol (DVD)                                                             18.97    0.2                                            2-chloro-4,4'-(dichlorovinylidene)                                                                  20.11    8.6                                            diphenol (CDVD)                                                               2,2'-dichloro-4,4'-(dichlorovinylidene)                                                             20.91    91.0                                           diphenol (DCDVD)                                                              2,2',6'-trichloro-4,4'-(dichlorovinyli-                                                             21.91    0.2                                            dene)diphenol (TCDVD)                                                         p-cumylphenol (reference)                                                                           12.36                                                   ______________________________________                                    

Incremental addition of 2.8 parts by weight of more chlorine raised theassay of dichloro-DVD (DCDVD) as follows:

    ______________________________________                                        Compound    Composition (Mole %)                                              ______________________________________                                        DVD         0                                                                 CDVD        2.2                                                               DCDVD       93.7                                                              TCDVD       4.1                                                               ______________________________________                                    

Washings of the nearly colorless methylene chloride solution with waterproduced a yellow methylene chloride solution that was separated fromthe aqueous phase. Circa one-fourth of its volume of methanol was addedto it and decolorized by stirring the yellow solution with 5 parts byweight zinc powder for about 1 hour. Filtration and evaporation of thesolvent mixture on a rotary evaporator left behind a white crystallinemass that was recrystallized from a mixture of hexane and cyclohexane(1.0:1.5 volume ratio). The colorless crystals of2,2'-dichloro-4,4'-(dichlorovinylidene)diphenol thus obtained had anassay of 99.1% and a melting point of 110.0°-110.5° C. Elementalanalysis confirmed its composition. Chlorine: found, 40.6; theoretical,40.5%. Carbon: found, 48.0; theoretical, 48.0%. Hydrogen: found, 2.2;theoretical, 2.3%.

EXAMPLE 2 Preparation of the polycarbonate of2,2'-Dichloro-4,4'-(dichlorovinylidene)diphenol

Into a mixture of 87.5 parts by weight (0.25 partmole)2,2'-dichloro-4,4'-(dichlorovinylidene)diphenol (DCDVD), 300 parts byvolume water, 300 parts by volume methylene chloride, 0.47 parts byweight phenol and 0.5 parts by weight triethylamine, there wasintroduced, at ambient temperature, 30 parts by weight phosgene in 30minutes while maintaining the pH value of the two-phase system atapproximately 11 (between 10 and 12.5) by simultaneously adding a 25percent sodium hydroxide solution. At the end of the addition period,the pH of the aqueous phase was 11.4 and the DCDVD content of this phasewas less than 1 part per million, as determined by ultraviolet analysis.The methylene chloride phase was separated from the aqueous phase,washed with an excess of dilute (0.01 normal) aqueous hydrochloric acid,and three times with deionized water. The polymer was precipitated byadding the neutral and salt-free methylene chloride solution to anexcess of methanol and filtering off the white polymer, which was driedat 95° C. The resultant pure DCDVD polycarbonate had the propertiesshown in the Table.

EXAMPLE 3

The procedure of Example 2 was repeated except that DCDVD was replacedwith a mixture of 43.75 parts by weight DCDVD (0.125 partmole) and 28.5parts by weight 4,4'-isopropylidenediphenol, (BPA) (0.125 partmole).Work-up of the reaction product yielded a copolycarbonate with theproperties shown in the Table.

EXAMPLE 4

The procedure of Example 2 was repeated, except that DCDVD was replacedwith a mixture consisting of 21.9 parts by weight DCDVD (0.0625partmole) and 42.75 parts by weight 4,4'-isopropylidenediphenol (BPA)(0.1875 partmole). The resultant polycarbonate had the properties shownin the Table.

EXAMPLE 5 Preparation of a New Ternary Composition

The procedure of Example 1 was repeated except that 71.0 parts by weight(1.0 partmole) chlorine was employed. At the end of the reaction, gaschromatographic analysis indicated the following composition:

    ______________________________________                                                            Retention  Compo-                                                             Time       sition                                         Diphenol Compound   (Min.)     (Mole %)                                       ______________________________________                                        4,4'-(dichlorovinylidene)phenol                                                                   20.80      28.7                                           2-chloro-4,4'-(dichlorovinylidene)                                                                22.34      45.2                                           diphenol                                                                      2,2'-dichloro-4,4'-(dichlorovinylidene)                                                           23.52      26.1                                           diphenol                                                                      p-cumylphenol (reference)                                                                         15.32                                                     ______________________________________                                    

EXAMPLE 6

The procedure of Example 2 was repeated except for substituting anequivalent amount of the ternary mixture (78.9 parts by weight) obtainedin Example 5, for the 87.5 parts by weight of DCDVD. A colorless, toughpolycarbonate was obtained having the properties set forth in the Table.

EXAMPLE 7 Preparation of a New Compound:2,2'-Dibromo-4,4'-(dichlorovinylidene)diphenol

The procedure of Example 1 was repeated, except that the chlorine gaswas replaced with an equivalent amount of liquid bromine (320.0 parts byweight, 2 partmole), diluted with five fold its volume of methylenechloride. After decolorization with zinc powder and purification bycharcoaling a white crystalline mass, comprising2,2'-dibromo-4,4'-(dichlorovinylidene)diphenol was obtained that, afterrecrystallization from a hexane-cyclohexane mixture (1:1) yielded whitecrystals of 97.8% purity and 107.5°-108.5° C. melting point. Elementalanalysis confirmed the composition. Chlorine: found 16.1; theoretical,16.2% Bromine: found 36.6; theoretical, 36.4%. Carbon: found, 38.1;theoretical, 38.3%. Hydrogen: found, 1.8; theoretical, 1.8%.

EXAMPLE 8

The procedure of Example 2 was repeated except that 109.7 parts byweight (0.25 partmole) of 2,2'-dibromo-4,4'-(dichlorovinylidene)diphenolwas used in place of DCDVD. A polycarbonate was obtained having theproperties set forth in the Table.

                  TABLE                                                           ______________________________________                                        Properties of Polycarbonates and Copolycarbonates                                            UL Rating                                                      Example        Specimen Thickness                                             No.       I.V.     1.56 mm    3.13 mm  WVTR                                   ______________________________________                                        2         0.55     V-O        V-O      1.4                                    3         0.588    V-O        V-O      3.3                                    4         0.592    V-O        V-O      6.1                                    6         0.576    V-O        V-O      1.8                                    8         0.482    V-O        V-O      3.0                                    ______________________________________                                    

As the results in the foregoing table reveal, excellent flame retardanceis imparted to the polycarbonates and copolycarbonates of the inventionwhile concurrently improving their water vapor transmission properties.

What is claimed is:
 1. A high molecular weight aromatic polycarbonatehaving improved flame retardance and improved water vapor transmission,said polycarbonate having an I.V. of about 0.40-1.0 dl/g. and beingrepresented by the general formula ##STR3## wherein Xm and Xn can eachindependently be a halogen and mixtures thereof; m and n are each 0.0 toabout 2.5 with the proviso that m+n equal at least 0.1, but no more thanabout 2.5 and, Y and Y' can independently be hydrogen and a halogen. 2.The polycarbonate of claim 1 wherein Xm and Xn are each chlorine.
 3. Thepolycarbonate of claim 1 wherein Xm and Xn are each bromine.
 4. Thepolycarbonate of claim 1 wherein m+n equal 1.5.
 5. The polycarbonate ofclaim 1 wherein Y and Y' are each hydrogen.
 6. The polycarbonate ofclaim 1 wherein Y and Y' are each chlorine or bromine.